fix linter warnings and some headers

[conao3]

Hi! I found many linter warnings so I try to solve them. But many warnings remained. I fix easy warnings only.

Warnings

Lisp symbol ‘regexp-opt’ should appear in quotes (emacs-lisp-checkdoc)
Lisp symbol ‘regexp-quote’ should appear in quotes (emacs-lisp-checkdoc)
Lisp symbol ‘text-mode’ should appear in quotes (emacs-lisp-checkdoc)
Name lisp should appear capitalized as Lisp (emacs-lisp-checkdoc)

Headers

Some headers wrote Created date as -- format. Follow smartparens.el.

Fix header comment to follow smartparens.el

Remove unneeded version/keyword/url comment header (should refer main smartparens.el).

[conao3]

I reverted your mentioned diff. There are any other concerns?

[Fuco1]

I'll need to do another review, it's a huuuge change set. Thanks for your patience!

[conao3]

Thanks reply! It's just a ping. I thank you very much for maintaining many packages.

[conao3]

Any concerns?

[Hi-Angel]

The list of warnings that is in the PR description should go instead to the commit message body. Because once it's merged, it's highly unlikely anybody's gonna read the PR, but people do read git-log.

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With that said, @Fuco1 ping? I also noted that smartparens produces various warnings with native compilation, I think this PR would be a good start (even though I presume it doesn't fix byte-compilation warnings)